Process and apparatus for cleaning rigid objects



April 3, 1962 G. EDHOFER ET AL PROCESS AND APPARATUS FOR CLEANING RIGID OBJECTS Filed May 26, 1959 INVEN TORS 66006 EOHOFE)? HA ms H6 u. eqsxa K Qr ees/MP7- Enwar 500410 1' United States Patent 3,028,267 PROCESS AND APPARATUS FOR CLEANING RIGID OBJECTS Georg Edhofer, Hanns Hiillerer, Kurt Lebsanft, and Ernst Schmidt, lvlunich, Bavaria, Germany, assignors to Wacker-Chemie G.m.b.H., Munich, Bavaria, Germany, a corporation of Germany Filed May 26, 1959, Ser. No. 815,929 Claims priority, application Germany June 13, 1958 6 Claims. (Cl. 134-7) This invention relates to cleaning rigid objects such as metal plates, castings, etc., which have become contaminated with grease, oil, dirt, metal shavings and the like, and it has for its object to provide a novel and improved process and apparatus for cleaning such objects.

Another object of the invention is to expedite the complete removal of soluble and insoluble dirt and other irnpurities from objects of the above type and to etfect a considerable saving in the cost of the cleaning operation.

Various other objects and advantages will be apparent as the nature of the invention is more fully disclosed.

It is a common practice to clean all sorts of objects with chlorinated aliphatic hydrocarbons such as trichlorethylene, perchlorcthylene and the like. To cite just one example, polished brass plates which have been lying around a factory or warehouse, and have become encrusted with grease, dust and dirt, must be thoroughly cleaned before they can be fabricated into bright, shiny radio panels, etc., and the above-mentioned cleaning fluids have frequently been used for such purpose.

In cleaning such objects, as Well as many others, it is also a well-known practice to mix finely distributed insoluble solids or fillers, such as ball-shaped particles of polyvinyl chloride, or cellulose acetate in flakes and powder form, with the liquid solvent in order to increase the iubbing and cleaning effect. In this Way it is possible to remove from the objects to be cleaned, not only soluble impurities such as grease, oils, etc., but also insoluble impurities such as grinding dust, metal shavings and the like.

Especially in large-scale cleaning operations of the above type, the objects to be cleaned are conveyed through various cleaning and washing chambers, the first oi which may contain fillers of the type mentioned while one or more succeeding chambers may contain only the liquid solvent. In practice, however, it has been found that the first chamber quickly get-s soiled with all kinds of dirt, which necessitates frequent changing of the solvent and cleaning or replacement of the soiled fillers.

It has also been known for a long time to degrease metals, etc, by means of solvent vapors. Such a process is capable of achieving complete degreasing and de-oiling, but the hard solid impurities which adhere to the objects to be cleaned, such as metal shavings and dust formed in wire-drawing operations, etc., remain clinging to the objects, just as do polishing and grinding particles after treatment with pastes. In order to do a thorough vapor cleaning job, even today objects of the above type have to be given a final manual treatment by wiping them with a cloth or rubbing them with sawdust.

We have now discovered that the foregoing shortcomings of the prior art can be avoided by a rapid continuous process and apparatus in which the objects to be cleaned are first degreased by the vapors of a solvent containing fillers, and only then, While said objects are still moist with the solvent, are the objects immersed in the liquid solvent containing the fillers, and, subsequently, in washing chambers containing liquid solvent without fillers.

An important advantage of the invention resides in the fact that during the initial treatment of the objects with the solvent vapors, the major quantity of dirt and grease 3,028,257 Patented Apr. 3, 1962 rice removed by the condensate dripping off the treated ob jects does not get into the chamber containing the tillers, but is deflected away from said chamber by a drip shield or pan and the soiled condensate conducted away for distillation. Thus the filler chamber, in which the initially degreased objects are next immersed, remains absolutely free of grease and oil, assuring its greatly prolonged period of use.

The above-mentioned step of degreasing and de-oiling may be performed directly over the filler chamber, the area above said filler chamber being filled with solvent vapors as hereinafter described, For this purpose a hinged sloping drip pan is mounted above the filler chamber and shields the entire area of said filler chamber while the degreasing step is taking place. During degreasing the dirty condensate is intercepted by the drip pan and flows down into a collection gutter. After degreasing, the hinged drip pan is raised to a vertical position and the entire area of the tiller chamber thus becomes unobstructed for the immersion of the already degreased objects to be cleaned.

The filler-containing solvent in the filler chamber is kept in motion, preferably by boiling, and, when the object to be cleaned is immersed therein, the rubbing action wipes of? theremaining dirt, etc, which was not removed by the initial degreasing step. The boiling solvent in the filler chamber also provides the solvent vapor which serves forthe preliminary degreasing and for keeping the treated objects moist.

After treatment in the filler chamber the objects being cleaned are washed in one or more solvent chambers, and the solvent in the last of said chambers is preferably cooled in order to provide a repeated washing by the condensation of the solvent vapors. If desired, the objects can then be sprayed or pressure Washed with clean solvent which may be obtained by distilling the dirty solvent removed during the degreasing operation.

The invention is described more in detail in connection with certain preferred embodiments illustrated in the accompanying drawing, in which:

FIG. 1 is a diagrammatic longitudinal sectional view of a preferred apparatus embodying the invention; and

FIG. 2 is a similar view illustrating a modification of the invention.

The apparatus shown in FIG. 1 comprises a vessel -1 which is sub-divided transversely into three cleaning chambers 2, 3 and 4, all of which contain a liquid solvent,

preferably a chlorinated aliphatic hydrocarbon such as trichlorethylcne or perchlorethylene.

The chamber 2, which We call the filler chamber, also has suitable filler particles suspended in the liquid solvent. For example, the solvent in chamber 2 may contain about 5% by weight of ball-shaped particles of polyvinyl chloride (average molecular weight 47,000) of 0.5-1 mm. diameter.

The solvent in filler chamber 2 is heated in any suitable manner, for example by a heating coil 5. When the temperature of the solvent is raised to the boiling point, it is agitated and this agitation efiects a distribution of the polyvinyl chloride particles throughout the chamber. The boiling of the solvent in chamber 2, and also in chamber *3 if desired, causes vapors of said solvent to fill the vapor zone 6 in the vessel 1 above chambers 2, 3 and 4.

A cooling device or coil 7 is mounted in vessel 1 above chambers 2, 3 and 4 for the purpose of condensing the solvent vapors in the upper part of vessel 1 so that the liquid condensate will drop back into the chambers. This cooling device is placed at such a height above the liquid surface in chamber 4 that the height of the vapor zone 6 corresponds with the immersion depth of the liquid solvent in the chambers. As illustrated, the chambets 2, 3 and 4 are of progressively increasing height, and any excess of the overflow from higher chamber to lower chamber may be drawn off through escape pipe 8 adjacent the top of chamber 2.

The downwardly sloping drip shield or pan 9 mounted above filler chamber 2 is hinged at 10 to the chamber wall so that said shield may be swung upwardly by any suitable means, such as a handle outside the vessel 1, to completely uncover the chamber 2. An object to be cleaned, such as a metal plate 12, is shown in FIG. 1 suspended by a chain or wire 13 held by the hand or by an automatic conveyor directly above the drip shield 9 in the vapor zone for the initial step of degreasing. The condensate dripping ofi the object 12 flows down the shield 9 into the gutter 14 and is conducted through pipe 15 into the distillation vessel 16.

After the object 112 has been treated a few seconds in the vapor zone, drip shield 9 is swung upwardly on its hinge 10, uncovering the filler chamber 2, and the object 12 is immersed either manually or mechanically in the solvent in chamber 2 for a few seconds and then withdrawn substantially free of dirt and foreign particles. The said object is then successively immersed in and removed from the solvent in chambers 3 and 4, where a few seconds washing removes every vestige of foreign matter. While drip shield 9 is being raised, the object 12 may be moved momentarily to a position over chamber 3, out of the way of said shield. The solvent in the final washing chamber 4 may be cooled as by means of a cooling coil 17.

FIG. 2 shows a modification of the invention in which the object 12 to be cleaned is initially degreased in a special vapor treating area 6a constituting a forward extension or continuation of the vapor zone 6. In this embodiment, the dirty condensate dripping from the object 12 flows into a collecting funnel 18 from which it is conveyed by pipe 19 to the distillation vessel 16. In other respects the process and apparatus are as described in connection with FIG. 1.

As stated above, the boiling of the solvent in chamber 2 causes said solvent and the fillers therein to be agitated, which expedities the cleaning operation. However, the solvent in this chamber as well as in the other chambers may also be agitated mechanically or electrically as by audible or inaudible sound waves, if desired. The objects being cleaned may also be agitated in any suitable manner to supplement the normal agitation caused by dipping or plunging said objects into the successive batches of solvent.

Although certain specific embodiments have been shown and described herein for purposes of illustration, it will be evident to those skilled in the art that the invention is capable of various modifications and adaptations within the scope of the appended claims.

The invention claimed is:

1. Process for cleaning objects in a plurality of successive batches of volatile liquid solvent, which comprises continuously creating a vapor of said solvent in the zone above said successive batches of liquid solvent and continuously condensing said vapor to precipitate the condensate into said liquid solvent to replenish the latter, initially placing the object to be cleaned in said vapor zone above one of said batches of liquid solvent, intercepting condensed solvent precipitating from said obfeet and discharging same at a point remote from said batches of liquid solvent, and then, while said object is still moist with solvent, immersing said object in and removing it from said successive batches of liquid solvent.

2. Process according to claim 1, in which the liquid solvent in at least the first batch in which said object is immersed, is agitated.

3. Process according to claim 1, in which the first batch of liquid solvent in which said object is immersed contains a plurality of finely distributed particles of solid material.

4. Apparatus for cleaning objects comprising a vessel containing a plurality of successive chambers each adapted to contain a volatile liquid solvent in which said objects are adapted to be immersed, means for creating a vapor of said solvent in said vessel in the zone above said chambers, means for suspending an object to be cleaned in said vapor zone, and means in the vapor zone for collecting and removing to a point outside the vessel condensed solvent dripping from said object in said vapor zone, at least one of said chambers being permanently open at the top into the vapor zone.

5. Apparatus according to claim 4, in which said collecting means comprises a movable shield mounted above one of said chambers, and means for conducting liquid solvent from said shield to a point outside said vessel.

6. Apparatus according to claim 4, which has a preliminary vapor treating area, constituting an extension of the vapor zone above said chambers and disposed in advance of the first of said chambers.

References Cited in the file of this patent UNITED STATES PATENTS 1,938,841 Koch Dec. 12, 1933 2,344,247 Hopkins Mar. 14, 1944 2,732,322 Murray Jan. 24, 1956 2,802,758 Kearney Aug. 13, 1957 2,901,383 Lebsanft Aug. 25, 1959 

1. PROCESS FOR CLEANING OBJECTS IN A PLURALITY OF SUCCESSIVE BATCHES OF VOLATILE LIQUID SOLVENT, WHICH COMPRISES CONTINUOUSLY CREATING A VAPOR OF SAID SOLVENT IN THE ZONE ABOVE SAID SUCCESSIVE BATCHES OF LIQUID SOLVENT AND CONTINUOUSLY CONDENSING SAID VAPOR TO PRECIPITATE THE CONDENSATE INTO SAID LIQUID SOLVENT TO REPLENISH THE LATTER, INITIALLY PLACING THE OBJECT TO BE CLEANED IN SAID VAPOR ZONE ABOVE ONE OF SAID BATCHES OF LIQUID SOLVENT, INTERCEPTING CONDENSED SOLVENT PRECIPITATING FROM SAID OBJECT AND DISCHARGING SAME AT A POINT REMOTE FROM SAID BATCHES OF LIQUID SOLVENT, AND THEN, WHILE SAID OBJECT IS STILL MOIST WITH SOLVENT, IMMERSING SAID OBJECT IN AND REMOVING IT FROM SAID SUCCESSIVE BATCHES OF LIQUID SOLVENT. 